1. Field of the Invention
The present invention relates to an automatic tube circumference scanning apparatus that is suitable for use in a system for inspecting, repairing and cleaning horizontal tube groups, especially superheaters and reheater tubes in a boiler.
2. Description of the Prior Art
Regarding boilers for use in a power plant, in Japan it is obliged to perform routine inspections according to the Electrical Enterprise Law, and since it is necessary to stop operation of a boiler when a routine inspection of the boiler is carried out, it is a common practice to perform inspections and repairs other than the routine inspection items coincidently with the routine inspection. Among these other inspections and repairs, the inspection and repair of boiler superheater tubes are carried out by workers after setting up a scaffold.
The state of inspection and repair of the interior of a boiler is shown in FIG. 9 which is a longitudinal cross-sectional view, and in FIG. 10 which is a perspective view of a part encircled by line X in FIG. 9. In these figures, materials for setting up a scaffold are carried into a furnace c through a hopper b of a boiler a and a scaffold d is set up in the furnace. In this case, since the carry-in port for materials is limited to a narrow space such as the hopper b, the materials to be carried in must be formed as small as the size of the carry-in port, and also since introduction of a machine into the furnace is impossible, the setting-up within the furnace must entirely rely upon human labor, so that setting-up of the scaffold d necessitates a long period of time.
In addition, in the case where heat transfer tubes e are arrayed in the horizontal directions, workers conduct measurement and inspections while being positioned in a space between the tubes. Hence, the precision of such measurements is lowered due to bad environmental working conditions. Also, there are many places where measurements are impossible due to the narrow space, and reliability of the measurements is poor.